The object of the present invention lends itself to being used in the industrial field of machines and devices intended for making logs of tissue paper, like for example toilet paper, kitchen roll and/or similar.
In particular, the present invention concerns a device intended for gluing the final edge of logs of band-shaped material that must be structurally stabilised before carrying out the subsequent cutting step necessary for the formation of the end product.
As known, there are various gluing devices suitable for applying onto the outer surface of the logs being produced, along a direction parallel to the longitudinal axis thereof, a layer or film of glue able to fix the final edge of the band of paper supported, according to a stable position.
Generally, once the glue has been applied to the surface of the log being produced, the log and/or the final edge thereof are suitably manipulated to determine the adhesion of the final edge on the outer surface of the log provided with the glue previously applied, so that the final edge of the band of paper stays glued to the rest of the band supported and the log is ready for the subsequent cutting or punching step.
An example of the aforementioned devices for gluing the final edges of logs of paper is described and illustrated in document EP0481929.
In particular, the described device foresees a rolling plane on which the logs of paper being fed roll in the direction of the next work station. The rolling plane has a through opening through which a predefined quantity of glue is applied on the outer surface of the band of paper supported to ensure that the latter and its final edge are joined together.
The application of the glue is made possible by at least one tubular-shaped container communicating, through a series of holes, with a wedge-shaped upper space, the inclined walls of which define a slot disposed at the through opening of the rolling plane.
The container is connected to suitable means for inserting the glue that determine the overflowing of the latter through the slot of the wedge-shaped space, at the through opening of the rolling plane to engage the outer surface of the band carried by the log being fed.
Under the tubular container there is a collecting space for recovering the excess glue that falls during the production cycle of the logs.
According to a further example of the aforementioned devices for gluing the final edges of logs, described and depicted in document EP0699168, the application of the glue on the logs being fed is carried out through a mobile application blade that immerses, first of all, in the glue and then applies it to the outer surface of the supported band.
In particular, such a system also foresees a rolling plane intended to support the logs being fed. The rolling plane is provided with a through opening through which the aforementioned application blade is able to deposit a predefined quantity of glue on the outer surface of the band carried by the log being fed.
Under the through opening a housing container of the glue is defined that is continuously kept in a filled state.
The application blade is mobile, along a handling direction transversal to the rolling plane, between a first position, in which the application blade is entirely immersed in the glue contained in the housing container and a second position, in which at least one application edge of the application blade surfaces from the glue contained inside the housing container to be located at the through opening of the rolling plane.
The application blade is mobile by means of a suitable linkage that lies inside the housing container completely immersed in the respective glue.
A further device for gluing the final edge of logs is also known, which foresees the use of a fixed application blade on the application edge of which a predefined quantity of glue suitably picked up by a mechanical collecting member is deposited.
In detail, the mechanical collecting member is mobile between a first position in which it immerses into a glue that is housed in a corresponding container, and a second position, in which it is at a higher level with respect to the application edge of the fixed application blade. In such a position, the mechanical collecting member, by gravity, deposits the glue collected earlier on the application edge of the fixed application blade, said glue being prepared for the application step. Thereafter, the collecting member is taken back into the first position to collect the glue and free the rolling plane so that the log being fed can intercept the fixed application blade provided with the glue.
Although known devices for gluing the final edges of the logs of paper allow the stable adhesion of the final edge of the log to the outer surface of the respective band, the Applicant has found that they do nevertheless have some drawbacks and can be improved in various ways, mainly in relation to: the application speed of the glue, in other words the number of logs able to be processed by the devices per minute; the simplicity, practicality and speed of execution of the maintenance operations of the devices; the time and cost of the maintenance operations; the amount of glue used for the application operations of the glue on the logs being fed; as well as the manufacturing and/or marketing costs of the logs of paper produced.
In particular, the Applicant has found that known devices, during the application of the glue, have rather long processing times that have a considerable impact on the production and/or marketing costs of the logs produced.
This drawback can be observed, both in the vertical overflow and in the quoted mechanical application systems, which are limited, during the application of the glue, by its own structural configuration.
Specifically, the vertical overflow application system is subject to the slow introduction of the glue into the application container, by the insertion means.
With regard to the application system by immersion of the application blade, it is inevitably required to move it inside the glue, the density of which significantly opposes the movements of the application blade and of the linkage associated with it with the consequent slowing down of the application operation of the glue.
Similarly to the application system by immersion of the application blade, the system based on a mobile collecting member that immerses into the glue to deposit it onto a fixed application blade is also subject to the resistance of the glue itself.
It should also be considered that such a system is further slowed down by the depositing step, by gravity, of the glue previously collected, on the fixed application blade. Such an operation noticeably penalises the application operation of the glue in terms of processing time, since it requires waiting for the glue itself to fall from the mechanical collecting member to the fixed application blade.
It should also be considered that the maintenance of the mechanical systems for applying the glue is particularly laborious, requiring long time periods to carry it out that have an impact upon the manufacturing and/or marketing costs of the products. Specifically, since the mechanical application systems operate immersed in the glue, they require frequent and meticulous maintenance interventions aimed at ensuring its correct operation.
The maintenance of such members also requires considerable stopping times of the respective machine or production line. Indeed, carrying out such maintenance operations requires, first of all, the complete emptying of the housing container of the glue to make it accessible to workers and, then, the cleaning of the mechanical members involved that move the application blade.
In addition, the application devices quoted above require the presence of considerable masses of glue, both for the feeding of the containers in the vertical overflow systems, and for the immersion of the application blade or of the collecting member, in mechanical movement systems.
In addition, the presence of considerable masses of glue requires frequent maintenance interventions aimed at cleaning the spaces and the ducts dedicated to them, as well as the provision of particularly efficient systems for recovering and filtering the glue, intended to filter the glue that, coming into contact with the mobile mechanical members of the application blade, can become polluted and dirty.